varicella zoster virus varicella...

Varicella Zoster Virus

• Herpesvirus (DNA)

• Primary infection results invaricella (chickenpox)

• Recurrent infection results inherpes zoster (shingles)

• Short survival in environment

Varicella Pathogenesis

• Respiratory transmission of virus

• Replication in nasopharynx andregional lymph nodes

• Repeated episodes of viremia

•Multiple tissues, including sensoryganglia, infected during viremia

Varicella Clinical Features

• Incubation period 14-16 days(range 10-21 days)

•Mild prodrome for 1-2 days

• Rash generally appears first onhead; most concentrated ontrunk

• Successive crops over severaldays with lesions present inseveral stages of development

Herpes Zoster (Shingles)

• Reactivation of varicella zoster virus

• Can occur years or even decades afterillness with chickenpox

• Generally associated with normal agingand with anything that causes reducedimmunocompetence

• Lifetime risk of 20 percent in the UnitedStates

• Estimated 500,000- 1 million cases ofzoster diagnosed annually in the U.S

Varicella Complications

• Bacterial infection of skin lesions

• Pneumonia (viral or bacterial)

• Central nervous systemmanifestations

• Reye syndrome

• Hospitalization: 2-3 per 1,000 cases

• Death: 1 per 60,000 cases

• Postherpetic neuraligia (complicationof zoster)

Groups at Increased Risk ofComplications of Varicella

• Persons older than 15 years

• Infants younger than 1 year

• Immunocompromised persons

• Newborns of women with rashonset within 5 days before to 48hours after delivery

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5

10

15

20

25

<1 1-4 5-9 10-14 15-19 20+

Age group (yrs)

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Varicella Fatality Rate-United States, 1990-1994

*Deaths per 100,000 cases. Meyer et al, J Infect Dis 2000;182:383-90

Varicella Epidemiology

• Reservoir Human

• Transmission Airborne droplet Direct contact with lesions

• Temporal pattern Peak in winter and early spring (U.S.)

• Communicability 1-2 days before to 4-5 days after onset of rash May be longer in

immunocompromised

0

20

40

60

80

100

120

<1 1-4 5-9 10-14 15-19 20+

Age group (yrs)

Rate

*

Varicella Age-Specific IncidenceUnited States, 1990-1994

*Rate per 100,000 population. National Health Interview Survey data

Varicella in the United States

• Increasing proportion of cases area result of breakthrough infection

• Outbreaks reported in schoolswith high varicella vaccinationcoverage

• Persons with breakthroughinfection may transmit virus

Herpes Zoster

• 500,000 to 1 million episodesoccur annually in the UnitedStates

• Lifetime risk of zoster estimated tobe at least 20%

• 50% of persons living until age 85years will develop zoster

Varicella-Containing Vaccines

• Varicella vaccine (either alone orw/ MMR)

–approved for persons 12 monthsand older (only through 12 yearsfor MMRV)

• Herpes zoster vaccine approvedfor persons 60 years and older

(these contain the same vaccine,just different concentrations)

Varicella VaccineImmunogenicity and Efficacy

• Detectable antibody

–97% of children 12 months-12 years following 1 dose

–99% of persons 13 yearsand older after 2 doses

• 70%-90% effective againstany varicella disease

• 95%-100% effective againstsevere varicella disease

Varicella BreakthroughInfection

• Immunity appears to be long-lasting for most recipients

• Breakthrough disease muchmilder than in unvaccinatedpersons

• Recent evidence that risk ofbreakthrough infection increaseswith time since vaccination*

*Chavez et al. New Eng J Med 2007;356:1121-9

Varicella BreakthroughInfection

• Retrospective cohort study of 115,000children vaccinated in 2 HMOs duringJanuary 1995 through December 1999

• Risk of breakthrough varicella 2.5times higher if varicella vaccineadministered less than 30 daysfollowing MMR

• No increased risk if varicella vaccinegiven simultaneously or more than30 days after MMR

MMWR 2001;50(47):1058-61

Herpes Zoster Vaccine Efficacy

• Compared to the placebo groupthe vaccine group had:

–51% fewer episodes of zoster

–Lower efficacy for olderrecipients

–Less severe disease

–66% less postherpetic neuralgia

• Duration of immunity unknown

NEJM 2005;352(22):2271-84.

Varicella Vaccine RecommendationsChildren

• Routine vaccination at 12-15months of age

• Routine second dose at 4-6 yearsof age

•Minimum interval between dosesof varicella vaccine for childrenyounger than 13 years of age is 3months (otherwise 4 weeks)

Herpes Zoster Vaccine*

• Approved for a single dose amongpersons 60 years and older

•May vaccinate regardless of priorhistory of herpes zoster (shingles)

• Persons with a chronic medicalcondition may be vaccinatedunless a contraindication orprecaution exists for the condition

*provisional recommendations as of January 2007

Varicella Immunity*

• Written documentation of age-appropriate vaccination

• Laboratory evidence of immunity orlaboratory confirmation of disease

• Born in the United States before 1980

• Healthcare provider diagnosis orverification of varicella disease

• History of herpes zoster based onhealthcare provider diagnosis

*provisional recommendations as of January 2007

Varicella VaccineAdverse Reactions

• Local reactions (pain, erythema)

–19% (children)

–24% (adolescents and adults)

• Rash – 3%-4%

–may be maculopapular ratherthan vesicular

–average 5 lesions

• Systemic reactions not common

Herpes Zoster VaccineAdverse Reactions

• Local reactions - 34% (pain, erythema)

• No serious adverse reactionsidentified

Varicella-Containing VaccinesContraindications and Precautions

• Severe allergic reaction tovaccine component or followinga prior dose

• Immunosuppression

• Pregnancy

•Moderate or severe acute illness

• Recent blood product

Varicella-Containing VaccinesUse in Immunocompromised Persons

• Most immunocompromised personsshould receive varicella-containingvaccines

• Varicella vaccine may beadministered to persons withisolated humoral immunodeficiency

• Consider varicella vaccination forHIV-infected children with CD4% of15% or higher

Varicella-Containing VaccineStorage and Handling

• Store frozen at 5°F (-15°C ) orlower at all times

• Store diluent at roomtemperature or refrigerate

• Discard if not used within 30minutes of reconstitution